The present invention relates to radio communications, and more particularly, to mobile communications networks and devices providing positioning.
In mobile communications networks, user terminal positioning may be used to support emergency services so that a precise location of a calling user terminal may be automatically determined and provided to an emergency responder (e.g., a paramedic ambulance service, a police department, a fire department, etc.). The U.S. Federal Communications Commission (FCC), for example, is requiring that a mobile communications network automatically provide a precise location for cellular radiotelephones placing an emergency 911 call. Such positioning may also be used for non-emergency services such as navigation, location aware computing, network optimization, resource management, etc.
For example, GPS (Global Positioning System) may be used to locate a user terminal using GPS satellite signals received at the user terminal. GPS positioning, however, may require inclusion of a separate GPS receiver, and/or GPS positioning may not be available indoors and/or in an urban canyon. Other positioning techniques may use terrestrial mobile communications networks. With Observed Time Difference Of Arrival (ODTA), for example, the user terminal measures time differences between positioning reference signals received from different cells (base station transmitters), and the measured time differences are used to determine a position of the user terminal. With Assisted-GPS (A-GPS), the terrestrial mobile communications network is used to improve GPS receiver performance by providing satellite constellation information to the GPS receiver. With Cell-ID, a rough user terminal position may be determined based on a cell sector being used by the user terminal during an active call. These and other positioning techniques are discussed in the reference by Guolin Sun et al., entitled “Signal Processing Techniques in Network-Aided Positioning [A Survey of State-of-the-art Positioning Designs]” (IEEE Signal Processing Magazine, pages 12-23, July 2005), the disclosure of which is hereby incorporated herein in its entirety by reference.
Notwithstanding known positioning techniques, there continues to exist a need in the art for improved positioning techniques, for example, providing increased speed and/or efficiency.